The present invention relates to optical lenses and in particular to lenses comprised of more than one layer, and wherein a Fresnel type configuration is a part of the lens.
In the past, optical lenses of the so-called spectacle or eye-glass type to correct various visual defects have been relatively thick and heavy. Accordingly, an object of the present invention is to provide a lens which is thinner and less weight than a conventional lens, and which still has high qualities and standards of optical characteristics.
U.S. Pat. No. 3,383,676 illustrates a lens comprising a two-piece element having interfitting surfaces and having a Fresnel-type formation only on an exterior surface of one of the elements which focuses on a common point on one side of the lens. The interfitting surfaces form an array of individually complete lenses which focus on individual points on the other side of the lens. The lens series derives its optical characteristics from the optical densities of materials and the Fresnel lens derives its optical characteristics from the refractive index of only one of the elements. In the invention of the present application the optical characteristics depend upon the refractive indices of mating Fresnel lens elements of optically different materials.